Sharing radio network hardware enables network operators to share the usually heavy deployment costs of cellular radio communication networks. It is possible today to share much of the Base Station System (BSS) hardware of a GSM network, including Base Station Controllers (BSCs), physical base station sites, Radio Base Stations (RBSs), RBS antennas, etc. Thus, a BSC and an RBS can be configured to support multiple cells that belong to different operators, or Public Land Mobile Networks (PLMNs), which are identified by different Mobile Network Codes (MNCs).
Each RBS in a BSS shared by different PLMNs broadcasts a respective one of the different MNCs, and so only mobile stations (MSs) registered in an operator's core network (and MSs from roaming partners of the operator) can access that operator's RBS. It may be noted that an MS's Home PLMN is the PLMN where the Mobile Country Code (MCC) and MNC of the PLMN identity are the same as the MCC and MNC of the MS's International Mobile Subscriber Identity (IMSI)
Hardware sharing is limited today. For example, the specific RBS hardware related to a cell, i.e., the radio transceiver (TRX), must be dedicated to a respective cell in a respective PLMN, and so TRXs cannot be shared. This is disadvantageous because although it is possible to share BSS hardware other than the RBS TRXs, the TRXs are a significant fraction of the total cost of an RBS. By not sharing TRXs, it is also not possible to even out the traffic loads between sharing PLMNs at busy times, and so each PLMN has to dimension its TRXs and RBSs for its own traffic peaks.
U.S. Patent Application Publication No. US 2010/0330996 A1 by Svedevall et al. (Dec. 30, 2010) describes a control node that enables operators to share BSS hardware by handing over an on-going MS connection between PLMNs of BSS-sharing operators. This is sometimes called inter-PLMN handover, and involves handing over an MS's circuit-switched (CS) connection from a cell, or RBS, belonging to a first operator to a cell, or RBS, belonging to a second operator, while the MS remains connected to the first operator's GSM core network. Also, a packet-switched (PS) connection can be handed over to a cell belonging to the second operator, while remaining connected to the first operator's General Packet Radio System (GPRS) core network. Although inter-PLMN handover can provide load sharing between cells from different PLMNs, it can be said that it does not effectively provide TRX sharing.